Telephone-exchange system



April 14, 1925. 1,533,182

C. L. G'QODRUM TELEPHONE EDKGHANGE SYSTEM Filed July 26, 1922 9 Shee //7|/6/7/5/-' Char/es L. 6004/0/72 April 14, 1925. I 1,533,182

' C. L. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed July 26, 1 9Q22 9 Sheets-Sheet 2 c. 1.. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed July 26, 1922 Q-Sheets-Sheet s hven/n- Char/as L. Good/um April 14, 1925. 1,533,182

c. L. GOODRUM TELEPHONE EXCHANGE SYSTBI Filed July 26, 1922 9 Sheets-Sheet 5 r hven/bn- Char/e3 L. G0 aid/um.

April l4, 19 25. 1,533,182 c. L. GOODRUM TELEPHONE EXCHANGE SYSTEM fivven/ar: Chm ks L. Gaoa/rum.

April 14, 1925.

C. L. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed July 26 1922 9 Sheets-Sheet '7 A ril 14, 1925. 1,533,182

' C. L. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed July 26. 1922 9 Sheets-Sheet 8 6724/ /25 A. Gaadn/m April 14, 1925. 1,533,182

v c. L. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed July 26, 1922 9 Sheets-Sheet 9 //1ve/1/0r. Ghak/es L. Good/um.

y' ig/7y To all, whom it may concern:

Patented Apr. 14, 1925.

PATENT OFFICE.

CHARLES L. eoonR-Uivr, 0F NEWY RK, N. Y.. ASSIGNOR T0 WESTERN ELECTRIC COM- .JPANY, mconronawnn ornnw YORK, NJYQ, A CORPORATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

Application filed July 26, 1922. Serial No. 577,504.

Be itknown that I, CHARLES LANE Goonman la citizen of the United States, resid ing. at New York, in the county of New York and State of New York, have invented certain new and useful, Improvements in Telephone-Exchange Systems,of which the following is asfull, clear, concise, and exact description. A a

This invention relates in general to telephone exchange systems.- More particularly, it has to do with telephone systems of the class in which machine switching, apparatus'is employed entirely or in part for the establishment of conversational connections.

The invention has for its objects to simplify the construction and operation of systems of the .foregoingcharacter to increase their flexibilityv and to render them more economical to produce, more dependable in their functions and of greater serviceahility. These objects are attained through the use of a new and improved type of selective switching medium controlled in accordance with designations to. cause the selective extension of conversational connections.

" A feature of the invention relates to a sit-itching mechanism for connecting inconr ing circuits to groups of outgoing circuits and having operating members, each se-Iving a group and capable of establishing a plurality of coexisting connections between the incoming circuits and the circuits of the corresponding group, together with designation controlled means for selecting said groups.

rr'nothe'r feature relates to a switching device of this character having links or intermediate circuits for interconnecting the incoming circuits with the groups of outgoing circuits and having cooperating switching members controlled by designation means for selecting the outgoing groups. g

A further feature relates to an improved testing arrangement for the switches of this general class whereby a selected group of outgoing circuits may be tested to'choosean idle one. a a

These and such other features and advantages as are contemplated by the present invention will become more clearly understood from the detailed description given Figs. 1 to 8 inclusive, order illustrated in Fig. disclose a portion of a telephone scheme system embodying the principles of this invention;

Fig. 1 shows a plurality of subscribers lines leading to the central office and terminatingin a preliminary or line switch ofthe particular type employed as a connecting medium in this system.

Fig. 2 shows a first group selector switch in which the trunks leading from the line switch in Fig. l terminate. This figure also discloses a plurality of groups of trunks out-going from the group selector switch.

Fig. 3 illustrates a sender selector switch serving in common a plurality 'of trunks interconnecting the line switch and group se lector switch of Figs. 1 and 2 for connecting any one of these trunks to one of a number of common sender mechanisms. F urthermore, this figure shows a set of common testing relays and a group marker device.

Fig. 4 shows one of the common sender mechanisms together with a marker device for determining the group selector switch involved in the connection.

Fig. 5 illustrates a second group selector switch substantially similar to the switch shown in Fig. 2 and which receives trunks incoming from said first group selector.

Figs. 6 and 7 correspond substantially to Figs. 3 and l and illustrate a'sender selector switch and one of a number of common senders located at the second selecting stage.

Fig. 8 shows a trunk leading from the second group selector switch which may extend through any number of succeeding group selectors. This figure also shows in diagrammatic form, a final or connector switch together with a called subscribers line.

Fig. 9 is a perspective view showing the structure and mechanical principles of the switching device employed for establishing connections in this system.

General description of the system and apparatus.

The switchingmechanisms shown in Figs. 1, 2, 3, 5, 6 and 8 are of the coordinate type in which incoming circuits appearing in rows of contacts are connectablc through link circuits to outgoing circuits also appearing in rows of contacts. The mechanical details of these switches, which are illuswhen arranged in the individually to the same cults.

trated in and will be later described in connection with 'F1g.'-9, are substantially the same as those of the switching devicerlis...

closed and described in the British patent to Western Electric Company, Limited,. No. 183,438, accepted September 6, 1923.

Considering the circuit arrangement ta switching mechanism when applied to a preliminary or line switching stage illustrated in Fig. 1, the subscribers lines 130,

10 1, 1.13, 131, etc. appear in rows ot-condiffering from the link circuits to which each of the other linesof the same row has access. For example. line 130- has'access to a group of link circuits 109, 110. etc. .therc being any desired number of these links. Line 113 in the same vertical row has access' to a different group o't links 111, 112, etc In like fashion, corresponding lines of the remaining vertical rows have access groupsof link cir- On the outgoing end ot the line switch,

' which has bcen generally designated by the character 100, a number of trunk circuits, o'tn'liicl1 the two trunks 114 and 115 are shown, eachhas access to all link circuits in all groups. That is to say, the trunk 114 occupies the whole vertical row 125 and is accessible to every link, 109, 110, 111 and 112 in the switching device. The circuit arrangement and operation of the line switch 110 above briefly outlined is substantially the same as that disclosed in the above mentioned British Patent No. 183,438, accepted September 6, 1923. lVhile the same mechanical construction is retained for the switching mechanism when employed as a selector as show-n in Fig. 2, the relative arrangement of the trunks and intermediate link circuits, the control of the =various elements due to the neccssity of selecting the groups and testuse of the mechanism as a line switch- In ing in a group andcertain other-features of operation, differ from those found in the l ig. 2, the first group selector switch 200, like 5 the line switch 100,.comprises a plurality of links orintermediate lines 206, 207, 208 and 209, the number of these being taken to suit requirements. The incoming trunks 114, 115, etc. whichlead from the lineswitch each occupies a, complete vertical-row I 201;and 2020f tbegro'up selector switch 200,

That is to say, the trunk 115 has a set of contacts cooperating with a corresponding set .of contacts on each of every intermediate link in .the switch 200 and the same is true for all, other trunks incoming to the switch. Ifdesir'able, theinterme'diate links could be grouped as illustrated in Fig. 1. However,

these links in the group selector switch 200 are not ;roiuped fin vthe present arrangement,

tical row 205 contains the group of trunk lines 221, 222, 223, 224:, etc. The trunk 221 is accessible to the intermediate link 206 and only to this one, the trunk222 is" accescessible to the 111111208, etc. 'Likewise, each of the intermediate links 206, 207, 208 and 209has access to a single trunk in each of the remaining numerical groups represented by rows 203, 20 1 and so on.

The outgoing groups of trunks from the first group selector 200 extend and are-distributed as incoming trunk lines among a number of second group selectors 500 The particular second group selector switch 500 shown may receive the trunks incoming a numerical group at the switch 200. Other numerical groups o-tt-runks leading from the switch 200 will similarly appear as incoming trunks in :other group selector switches 500. The second group selector switch 500 is identical in arrangement and principle to the first group: selectors 200. 'llhetru-nk 221' shown in full which belongs to the .numeri 211 group occupying the numerical. row 205 at the switch 200 enters and occupies the vertical row 502 of the selector 500. The second trunk shown in the switch 500 may be another trunk belonging tothe same-numerical group as the trunk 221 or it may lead from adiftcrent selector The switch 500 also has a number of out? going vertical groups of trunk lines 503, 501 and 505 whicn represent the second switching stage in the system and which extend to succeeding group -selector switches. Although only two switching stages have been shown in detail, it. will be'understood that any number of succeeding group selecting stages may be provided. a

After the last group selecting stage, the final or connecting stage maybe provided for completing the connections to the called subscribers lines- For this purpose a switch otthe same general character may be emsible to'the link 207, the trunk line223 is ac- 'ploye'd, one of which, switch 800, is schematically shown in' Fig. 8, or switches of other types may be used if desired. In accordance with the usual well-known practice, the final connecting stage provides for two directive operations, one to select the group of lines andthe other to select the desired line in that group. It is not considered necessary to show in full, further group selecting switches or to illustrate the details of the switch when applied as a final connecting device; The principles of this invention are adequately disclosed in the remainder of the system.

Turning to the preliminary or line switching stage, it may be observed that there are a plurality of line switches similar to the switch 100 each of which has a number of outgoing trunks which may be distributed in any number of first group selector switches 200. Also, the trunks incoming to any selector 200 may lead from one or more line switches 100. A number of these trunks 114i and 115 interconnecting the line switches and first group selector switches are arranged to appear in the sender selector switch 300, the function of which is to connect these trunks to one of a number of common sender controlling mechanisms such as shown in 4. The sender selecting switch 300 is substantially identical in its arrangement of incoming circuits, links and outgoing circuits to the line switch 100. The total number of trunks'which enter the par ticular switch 200 from the line switches are assigned to the first two vertical rows 301 and 302 in the sender selector switch 300. The trunks 11st and 115, which leave the line switch 100 and enter the group selector 200, appear as illustrated in the vertical row 301 of the sender selector switch. The trunks which appear in the vertical row 303, such as trunks 331 and 332, extend either from the line switch 100 or from another similar line switch and appear as incoming trunks in another first group selector switch 200. In other words, if there are five first group selector switches 200 required to handle the traffic, then the trunks appearing in the sender selector switch 300 will likewise be divided into five corresponding groups, each group occupying, as explained, one or more vertical rows of contacts. The purpose of'this arrangement is to enable an identification of the particular switch 200 on which the calling trunk appears as will be understood more clearly hereinafter.

By means of the intermediate link circuits 306, 307,308, 309, etc., the incoming trunks at the sender selectorswitch have access to outgoing circuits 316 and 317 leading to ,cominon controlling sender mechanisms. The circuit 317 relates to the sender mechanism shown in Fig. 4. The purpose of these sender mechanisms is to receive the registration of a series of impulses representing the group of trunks wanted and to control the selection of such a group at the selector switch 200. In order to prevent interference in the selection of controlling senders, an extended starter wire ar 'angement is provided whereby the circuitrepresenting the first idle sender will be exclusively selected through an intermediate link.

The device 130 shown in Fig. -l is a marker for identifying the first group selector switches 200. This marker comprises a phe rality of multicontact relays 411, 4:12, 113, one for each of the several switches 200 at the first switching stage. The relay 411, for example, is individual to the particular switch 200 shown. Whenever a connection is directed to this selector switch over any one of the trunks incoming thereto and the common sender is connected to said trunk by the sender selector 300, the marker relay 411 is operated to associate said sender with the selector 200. Should the call he extended over a trunk appearing in some other selector then another of the multicontact relays 412, 4.13 operates to associate the common sender with such other selector switch.

The device 330 shown in Fig. 3 is also a marker consisting of a plurality of multicontact relays 318, 319, 320. Each of these relays is individual to a particular group of outgoing trunks at the selector switch 200 and when operated serves to associate the common group of relays also shown in Fig. 3 with said group of trunks. The multicontact relay 318 is individual to the group of trunks occupying the vertical row 205 and through its contacts connects the left-hand windings of the test relays 321, 323, etc., respectively, to the test wires of the trunks of said group. Similarly. the multicontact relay 319 is individual to the group of trunks occupying the vertical row 204 and in like manner connects the left'hand windings of the test relays to the test conductors of the respective trunks in said group. For each of the several group selector switches 200 there is likewise provided a marker device similar to the marker 33 The set of testing relays 32], 322, 323, 321 comprises a number of relays equal to the number of trunks in a group at the selector switch 200 and, likewise, equal to the num ber of horizontal or intermediate lines 206, 207, 208, 209. This set of test relays is common to all groups of outgoing trunks and. as explained, through the medium of the marker 330 may be definitely associated with any particular group of trunks desired for testing. The left-hand windings of the several test relays are for the purpose of testing the condition of the respective outgoing trunks in the group. The righthand windingsof the relays are for the purpose of testing the condition oi the intermediate is made both of the out 'oin trunk and lines at the switch 200. For instance, when the testing relay set is associated with the group of trunks 205, the leit-hand winding oi relay 3:21 is connected through the contact of relay 318 to thetest wire 224 of the trunk 2:21. The left-hand winding ot-the next, relay 322 is similarly connected to the test wire of the next trunk and so ,on for each of the remaining relays. The right,- hand winding of relay 321 connected to the contact oi relay 217, the winding oi which relay is, in turn, directly connected to the test wire of the inte-rn'iediate line 206. In like manner each of the ren'iaining relays 323 of the test set have their righthand windings correspondingly connected to the armatures ot relays 218, 219, etc. individual to thesuccessive intermediate links 207, 208, etc. 'lly this arrangei'nent a test also of the intermediate link which ms access to said out; iing trunk in order to determine wnotner either or neither is busy or both. I r 7 As will be brought out more clearly herematter, any one oi? the intermediate links 206', .207 may be taken for use in extending a connection to trunks ineach of several outgoing groups. lrlence, it nra occur that while 'sel ction is being made in the group 205, the outgoing trunk idle. while at-the. same time theintermediate link 206 is busy in connection with a call previously e2,- tended' to an outgoing trunk in some other group. Thus, it is impossible to obtain connection with the trunk 221, notwitln standing the fact that it is idle per se. For this reason, it is necessary to employ the double test feature above outlined whereby no outgoing trunk will be taken for use regardless ot its idle condition provided the corresponding intern'icdiatc link, which must extend theconuection thereto. is at the time engaged. 7

At the next group selecting stage represented by the single selector switch 500 there are provided a number of common senders, one of which isshown in F T, a sender selector switch 600 tor associating these senders with trunks 221, 531, etc. incoming to the switches 500' tron] lirst 'roup selectors 200 and the marker devices 731) and. 630 all or which are substantially the same as-above explained in connection with the lirst group switching stage. Before proceeding with i. detailed description of the operation, a brief explanation willbc given olthe mechanical construction of the switching levice employed asa connecting medium in this system. For this purpose, reference lS lliMlO to- Fig. S) which givesa perspective view oi a portion of the switching mechanism clearly illus trating the manner in which it operates.

' Considering the terminal portion of: the

switch, there are provided a plurality of in terniediate-.or horizontal-link circuits 900, 991, consisting each ot a numberot plain bare wire conductors. The horizontal link 900 includes as shown iour conductors 902, W73, 90 1 and 905 and the horizontal link 901 likewise .has four conductors 906, 907, 908 and 909-. As many of these horizontal links may be provided as necessary and each may have more or less than the number of conductors actually shown. These horizontal hare wire link circuits constitute the passive or stationary part of the terminal ar rangement. Regarding the switch in the cap-a 'itv of a selector as and the incon'iing trunks or circuits each constitute a vertical-row ott movable terminals occupying the full row and having access to all of the horizontal link-circuits. l igzO shows one'ot' these incoming trunks which. is made up-oi the tour conductors 910, 911, 912 and 91 This trunk has a set of movable bare wireterminal conductors 91st, 915, 916 and 917, connected to the respective conductors, and which extend through oblique af iertures in a movable insulating card 029 to'points where they cooperate with the respectiveconductors 902, 90?), 90st and 905 oi the horizontallink 900. Tue card 929 is supported on a spring 9&8 secured in the insulating block Elli) which also secures the movable terminals 914-, 915, 916 and 917. Normally the spring wire 9-718 holds the card 92!) in such a'position that the movable termimils-are out of engagement with the correspoinling stationary wire terminals of the link circuit 900.

The wires 910, 911, 912 and 91?) or the incomingtrunk also are provided with a second set :ot' similar movable wire terminals 918, 919-, SEQ-and 921 which extend through the insulating card 932 to a. point where they cooperate with the stationary wires 906, 907, J08 and $109 of the next horizontal link 901'. In liketashion, the incoming trunk conductors have a set of these movable terminals in the vertical row for every horizontal link circuit. Obviously, there will be one of these vertical rows ot contacts for each trunk incoming to the. switch.

in addition to the several vertical rows of incoming circuits each representing a single incoming trunk, there are provided a plurality of vertical rows of outgoing trunks as explained in connection with Figs. and 5. 'ln the structure iilrawing of Fig. 9, one such vertical row of outgoing trunks is illustrated, two'separate trunks in thisrow being shown. ()n of these trunks comprises conductors 922, 923. 925i. and 925 and has a set of movable wire terminals as shown e tending into operative relation to the corresoonding wire'terniinalso't the horizontal link 900. The second trunk, the conductors 926, 92'? and 928 of which are shown, has a V the respective wires and913 and controls corresponding set of movable wire terminals which extend into operative relation with of the second horizontal link 901. In like fashion, each of the remaining trunks in the group or vertical row willhave a set of movable terminals extending into cooperative relation with the remaining corresponding horizontal links. 'Foroperating and maintaining the ter minals to establish connection between incoming trunks, links and outgoing trunks, there are provided a plurality of operating members or bars, a bar being arranged to serve each of the several vertical and horizontal rows of contacts. The vertical bar 941 is individual to the vertical row representedby the incoming trunk 910, 911, 912 all of the movable contacts pertaining to this trunk. The next vertical bar shown, bar 942, is individual to the row of contacts belonging to the group ofontgoing trunks 922, 923, 92 1 925 and 926, 927, 928. The function of these vertical bars is to prepare the contacts for operation and after thecontacts have been operated said bars may restore ready to betaken again for use in preparing another set of contacts.

' or trunk connecting switch, as shown in containing the lines 922,

Fig. 1, it is obvious thatthe incoming sulr scribers lines appear in the vertical rows 923, 924, 925 and 926, 927, 928, while the outgoing trunks appear, as trunks 910, 911,912, 913, each occupying a full vertical row. Dependent upon the number of horizontal links re.- quired for serving each incoming subscribers line, said line may be provided with a variable number of movable wire terminals cooperating with the respective horizontal links. v a A. short description of the operation of the switch shown in Fig. 9 is given below.

Assume that it is desired to connect the incoming trunk or circuit 910, 911, 912, 913 to the outgoing trunk 922, 923, 924:. First a circuit closed for magnet 9 :3. which, through its armature 950, rotates the vertical bar 941. The flexible wires 931. 934, etc. attached to the bar 941 are carried by the rotation of said bar against the shoulders on the corresponding insulating cards 929, 932.. Since the horizontal bar 938 is in its normal position at this time, the flexible wire 931 passesover the top of the lever 951 and is stopped by the shoulder on card 929 immediately above the notch 930 in the said lever 951. Similarly, the flexible wires 93%, etc. pertaining to the remaining horizontal links are positioned with respect to their cooperating levers similar to lever 935.

At the same time a circuit is closed for the magnet 944. controlling the bar 9 12, individual to the vertical row of trunk contacts containing the contacts of the particular trunk 922, 923, 924:, 925 to which connection is desired. The magnet 941+, rotates the bar 942 and the flexible wires 953, 954, each individual to a set of trunk contacts, are moved against the insulating cards 940, 936, and into cooperative relation with the levers 952. 937, on the horizontal bars.

Thus, when the contacts of the incoming trunk and the contacts of the outgoing trunk are prepared, it is only necessary tooperate the. horizontal bar 938 pertaining to the outgoing trunk to bring about the connection. This is done by energizing the magnet 945 which notates the horizontal bar 938. The ba 938 carries the levers 951, 952, etc. upwardly. Since the flexible wires 931 and 953 have been positioned they are encountered by the levers 951, 952, and flexed upwardly against the movable insulating cards 929 and 9&0 respectively. The continued rotation of the bar 938 carries cards 929 and 940 to their extreme upward positions whereby the movable wire terminals of the incoming trunk and the outgoing trunk engage the corresponding passive wire terminals of the horizontal linkcircuit 900 and the connection is effected. The. condition of the switch when operated is seen by referring to the terminal set 918. 919, 920. 921 in the lower left corner of Fig. 9.

.Following this. magnets 943 and 9% may be released permitting the bars 941 and 942 to return to normal position. Since the wires 931and 953 are held by the notches in thelevers 951 and 953, they flex on the rcturn movementof the barsbut do not disenthe lower surface of the cards 929 and 9&0, respectively. In this way, the continued energization of the magnet 9*15 after the magnets 943 and 944 have been deenergized, maintains the established connect-ion, while the remaining flexible wires 93 t, 954 return to normal. Should another connection be desired over another trunk 926, 927, 928 in the same group controlled by the bar 9 2. it could he obtained by a reoperation of said bar and the use of another idle horizon tal link circuit90l without interference with the first established connection. The details otthis featurewill be brought out more clearly in connection with the circuit description.

lVhen the established connection is no wardly permitting the insulating --the 'sprii'ig conductors 931 and move away from the cards 929 and 940,

' such so that on a subsequent rotation of the as. Y contact of relay 105, conductor 120, winding 119, assuming the trunk 115 to be idle,

contact of cut otl relay 104:,

over the loop of the er contact of relay bar 938 they will not be encounter d unless previously positioned'by the vertical bars in], are.

' Detailed description of the operation.

"onsider now, that the subscriber of line .101 desires to obtain a conversational connection with the subscriber of line 801. The calling subscriber, on initiating the call closes a circuit from battery through the right-hand winding of line relay 105, inner conductor 103, line, conductor 102, out- 1041, left-hand winding of relay 105 to ground. Relay 105 operates and a circuit is closed from ground through the contact of one or more of the horizontal link magnets 106, 107, conductor 132, inner of the vertical row magnet 133, outer right contactof magnet 108 to battery. nets 108 and 133 are individual to the vertical rows 123 and 124, respectively, and serve to rotate thevertical bars, such as bars 94:1 and 942 of the structure shown in Fig. 9. Provided the magnet 108'is deenergized, indicating that no simultaneous call is being handled in the first vertical group, the circuit above traced is closed, and magnet 133 operates to position its bar. 'The magnet 133 on operating closes a circuit from ground through its inner right contact, front contact of relay 117, assuming the first trunk 114. to be busy, back contact of relay windingot the vertical trunkniagnet 118 to battery; Magnet 118 operates and in a similar manner prepares the vertical bar individual to the row 12ti. x

Thus, in response to the initiation of a call, the vertical bar pertaining to the group in whi'chthe calling line appears is rotated 'to'prepare the contacts of this line for connection to some idle-one of the horizontal links 109, 110 and also the vertical bar pertaining to the row 126 containing the contacts ot' the idle trunk has been rotated to prepare these contacts for connection with the same idle horizontal link. The contacts for eiiecting the connection are, however, not operated at this instant. Instead, the establishment of a connection through to the trunk 115 awaits the connection of that The ma-gtrunk through the sender selector switch 300 At the time the vertical magnet 118 oper;

ates a circuit is closed from ground through the left contact of said magnet, conductor 133, winding of the vertical row magnet 311, to battery. The selection of the magnet 311 indicates that the selected idle trunk 115 appears in the vertical row 301 of the sender selector 300' Magnet 311 energizes, rotates its associated barand also closes a circuit from ground through its left contact, conduct-or 334, front contact otrelay 313 (assuming the sender mechanism represented by the circuit 316 is busy), back contact of relay 315, winding of the vertical row magnet 314;,to battery. Magnet 314i energizes and prepares its associated operating bar. Magnet 311 also closes a circuit from ground through its left contacts, conductor 335, winding of the impulse relay 4:00 to battery. 3y this means, the relay $100 is operated well in advance of theextension of the calling line through to the'selected sender mechanism. Relay 4100'completes a circuit from ground through its front contact, winding of slow-to-release relay 101 to battery and this'latter relay operates.

The magnet 3L1 furthermore closes a circuit'trom ground through its left contact, conductor 336, outer right-hand contactof magnet 11S, conductor 131, normal contact and winding of the horizontal link magnet 337, to battery. It is assumed that the horizontal link 309 is idle at this time. The magnet 337 operates, rotates the associated horizontal bar to effect a connection between the conductors of the trunk 115 and the conductors of thecircuit- 317 leading to the sender mechanism through the medium of the link circuit 309. ln'nnediately that the contactsinvolved in this connection are closed. a circuit is established from battery through the winding and inner front contact of magnet 337, horizontal conductor 338, through the associated contacts to the conductor 339, left contact of relay 40 1 to ground. The magnet 337 is held in this circuit dependent upon the relay 101 in the sender inechanism.- T

Immediately that connection isextended through the sender selector switch 300, a circuit for operating the horizontal link magnet at the line switch 100 is established. Assuming the horizontal link 110 to be idle, this circuit may be. traced tronr battery through the winding and normal contact of magnet 106, outer tront contact ot relay 105, conductor 121. left contact or magnet 133, inner right front contact of magnet 118. conductor 135, lower normal contact of relay 232, conductor 235, horizontal conducto-r 333, conductor 339 and thence to ground astraced at the contact of relay 101.

The horizontal magnet 106 of the line switch operates in this circuit, rotates the associated operating bar and extends the calling line through to the trunk 115. Im-

right front contact of magnet 106, conductor 136, thence to the conductor 135 and from there to ground over the path previously traced. The magnet 106 in addition to the magnet 33? is held under the control of the relay 401 in-the sender.

The horizontal magnet 106 extends the start circuit through to the normal contact of the next horizontal magnet 10? so that subsequent calls may be served by the next link circuit. The cut-off relay 104 is also operated at this time in a circuit from battery through the winding of said relay, through the operated contacts of the switch to the grounded horizontal conductor 136. Relay 104 opens the circuit of relay 105 which becomes deenergized and in so doing opens the circuit of the vertical magnet 133. Magnet 133 releases and permits the associated operating bar to return to its normal position. Magnet133 opens the circuit of magnet 118 which likewise restores and permits its associated bar to return to normal. When the magnet 118 deenergizes, it opens the above traced circuit for the vertical magnet311of the sender selector switch. The magnet 311 on releasing opens the circuit of the vertical magnet 314. Magnets 311 and 314 permit their associated bars to restore. The connection of the subscribers line through to the selected sender is now held by means of the maintained energization of horizontal magnets 106 and 337. hen magnet 118 deenergizes a circuit is closed from battery through the winding of relay 119, inner right back contact of magnet 118 to the grounded conductor 135. Relay 11.0 operates and extends the'start wire on to the next idle vertical magnet. Similarly, magnet 314 of the'sender selector 300 on releasing closes a circuit from battery through the winding of relay 315, to the grounded conductor 339. Relay 315 extends the start wire on to the next idle; vertical magnet.

Before the vertical magnet 314 releases to open the initial energizing circuit of the pulse relay 400, the circuit for this relay in series with the calling snbscribens line is closed as follows: Battery, through the winding of relay 400, conductor 335, contacts of the sender selector switch, horizontal conduct-0r 340, contacts of the sender selector switch, conductor 342, uppermost contact of relay 232, conductor 138, contacts of the line switch 100, horizontal conductor 139, contacts of line switch 100, line conductor 103, line conductor 102, contacts of the line switch 100, horizontal conductor 140, contacts of said line switch, trunk conductor 137, inner upper contact of relay to ground.

The apparatus is now in condition to receive impulses and, accordingly, the calling subscriber manipulates his dial to transmit a number of impulses representing the first digit of the wanted number. Assume, for example. that the first digit of the desired number is 3. lVhen the calling line opens on the first impulse, the relay 400 releases its armature and a circuit is closed from ground through the back contact of relay 400, right contact of relay 401, conductor 416, lowermost back contact of counting rel, .105. winding of counting relay 406 to bat cry. Moreover, a circuit is closed by way of conductor 416 through the winding of relay 402 tobattery. Relay 402 operates and being slow-to-release maintains its cnergization during the brief interruptions of its circuit at the contacts of relay 400. Similarly, the relay 401 remains operated during the series of impulses. Relay 402 closes a circuit from battery through the winding of the slow-to-release relay 404, front contact of relay 402 to ground at the left contact of relay 401.

The counting relay 406 operates in the circuit traced and a circuit is completed from battery to the winding of relay 40F, winding of relay 405, contact of relay 406, conductor 417, to ground at the left contact of relay 401. Relay 405, however, remains shunted as long as the back contact of relay 400 is closed. When the line closes at the end of the first impulse and relay 400 again operates the shunt is removed from the winding of relay 405 and this relay operates and locks in series with relay 406.

In response to the next two impulses of the series, the counting relays 408, 407, 410 and 409 are operated in the manner similar to the operation of relays 406 and 405. After the impulse series has been transmitted and an interval elapses, the slow rclay 402 becomes deenergized and opens the circuit of relay 404. Relay 404, however, being slow-to-release, maintains its armature tor an interval.

Relay 402, on deenergizing, completes a circuit from battery through the winding of relay 403, back contact of relay 402, uppermost contact of relay 405, front contact of relay 400 to ground. Relay 403 operates and a circuit is closed from ground through the contact of said relay, conductor 414, contacts of selector switch 300, horizontal conductor 343, contacts of said selector switch 300, conductor 344, winding of multicontact relay 411 to battery. Relay 411 operates its contacts and thereby associates the conductors from the counting relays of the sender with the vertical group magnets 21.1, 212, etc. ot the particular selector switch 200 in which appears the trunk 115 involved in this connection. Relay 111 looks in a circuit through its winding and contact, conductor e17, to ground at the left contact of relay 101. 7

Relay e03 also completes a circuit from ground through its contact, conductor lld, conductor 4e18, contacts of switch 300, horizontal conductor 3&5, contacts of said switch, conductor 34:6, winding of vertical magnet 236 to battery. The magnet 2300perates the bar individual to the vertical row 202 in which the contacts of trunk 1 appear. This particular magnet is selected, as explained, by reason of the fact that the contacts in the vertical row 301 of the sender selector switch 300 are operated. Hadthe sender been seized through contacts of one of the horizontal links 306, 307 in the vertical row 301, then the magnet 210 at the selector switch 200 would be operated since in this case thetrunk 11% would be the one trunks ground,

3241, conductor involved. 1

lVith the first three pairs of counting relays o aerated and with the inulti-contact relay 1-11 energized, a selecting circuit is established as follows for selecting a particular vertical magnet 211, 212, 237 at the switch 200 which controls the vertical row representing the desired outgoing group of through the contact of relay 103, inner contact of'relay 4:05, upper tront cont-acts ot relays e07 and 409, upper back contact oi relay e19, conductor 420, contacts of relay 4511, conductor 121, thence in parallel through the winding of multicontact relay 318 and through the winding of the vertical magnet 211 to battery. The magnet 211 rotates the associated vertical bar and prepares the contacts of all ot the outgoing trunks in the group.

The multi-contact relay 318, which is individual to the group of trunks appearing in the row 205. operates and associates the common test relays with the trunks, respec tively, in-said group.

The apparatus 'is now in condition to make a test of the outgoing trunks. of the selected group and also of the horizontal link circuits. During this interval the relavetO C is maintaining its armature attracted. by reason of its slow-to-release character and does not close its contact until after the tests have been made and the idle trunk to be used is determined. illustration, it will be assumed that the trunk 22% is idle, trunks 223 and 222 are busy, trunk 221 is idle, and that the horizontal links 200 and 208 are busy while links 207 and'206 are idle. Since the horizontal link 209 is busy in connection with some other call a circuit is closed from battery through the right-hand winding of relay 3 1-6, contact of relay 220 to For the sake of.

gno und. Relay 220 is energized at this time in a circuit from l. atter v through its winding through the grounded horizontal conductor 238. 'llheretore. the relay becomes energized. Since'the trunk 223 is busy a ground potential exists on the test conductor 229 and a circuit may be traced from battery through the letthand winding of relay 32-3. conductor 34?, contacts of relay 318. conductor 3th to the grounded conductor 229. Relay 3L3 operates in this circuit. horizontal link 208, which has access to the, trunk 223, isjengaged, a circuit is closed from battery througl-i the right-hand winding otrelay 323, conductor 34-0 to ground at the contact of relay'219. Relay 219 is energized at this time in a circuit from bat tery through its winding to the grounded horizontal test conductor ot. the link 208. The test relay 323 in this manner has both or its windings energized, either of which is sutiicientto operate the relay. The next outgoing trunk 222 being busy, a circuit is closed from battery through the left-hand winding of relay 322, conductor 350, contact of relay 31S, conductor 351 to thegrouuded test conductor 230. Since neither the horizontal link 200 nor the trunk 221 is busy, the circuits for thewindings of relay 321. are held open and this relay remains deenergized. Y 7

It will a also be assumed that the two lowermost test relays 325 and 326, which correspond to two horizontal links and the respective trunks (not shown in Fig. are energized by reason. of the busy condition of said links and trunks. Thus, all otthe test relays shown, exceptrelay 321, are energize-d through one or the other or both of their windings, according as the represented outgoing trunk, the corresponding link is busy or both-are busy.

At the end of the interval necessary to the release of relay 10%, the said relay re? tracts its armature and a circuit is closed from ground through the contact of relay 403, conductor all, contact of relay atO-t, conductor 115, let't arinatures and front contacts 0t relays 326, 325, 32 1, and 322 in series, let't armature and back contact of relay 321, conductor 352, right-hand winding of the horizontal magnet; 213, to battery. Magnet 213 energizes and rotates the associated horizontal bar to operate the prepared contacts in the vertical rows 202 and 205. The operation of these contacts connects the trunk 11,? to the corresponding conductors of the link circuit 206 and connects the conductors of said link to the corresponding conductors of the. idle outgoing-trunk 221 in the selected group. Immediatelythat the horizontal magnet- 213 operates, it closes a holding circuit from battery through its right-hand winding and contact, conductor Moreover, since the too 239 through contacts of the relay 411, conductor 417 to ground at the left-hand contact of relay 401. This circuit holds the magnet .213 energized under the control of the sender shown'in Fig. 4.

Upon the release of relay 404 a. circuit is also closed from ground, the contact of relay 403, conductor 414, contact of relay 404, conductor 415, thence through the contact of relay 318, conductor winding of 00!), magnet 610 to battery. Since the multi contact relay 318, which is individual to the selected group of trunks, 1s operated,

explained.

The magnet 610 operates and prepares the vertical bar and also closes a circuit from ground through its left contact, conductor 632, front contact of relay (315 (assuming the sender represented by the circuit 618 to be'busy), back contact of relay '617, winding of the vertical magnet 616 to battery. The magnet 616 operates and prepares the operating bar associated with the vertical row 605 and individual to the sender mechanism illustrated in Fig. 7. The magnet 616 also closes a circuit from ground through its left contacts, conductor 633, winding of the impulse relay 700 to battery. Relay 700 operates and closes a circuit from ground through its front contact, winding of the slow-to-release relay 701 to battery. Thus, the relays-700 and 701 operate in advance of the time when the trunk 221 is extended through the sender selector switch 600 to the sender mechanism shown. I

Magnet 610 also completes a circuit trmn ground throi'lgh its left contact, conductor 634, right front contacts of relays 320, 325,

324, 323 and 322 in series, right back con- 'tact of relay 321, conductor 354, lower contacts of magnet 620, winding of said magnet to battery. In this manner the condition ot the test relays in Fig. 3 is used for determining the horizontal appearance of the selected trunk 221 in the sender selector switch 600. That is to say, since relay 321 representing the trunk 221 is idle, the en'- cuit above traced is extended over the right 'back contact of relay 321 to conductor 354 associated magnet 620 is operated in the circuit traced and rotates the horizontal bar to actuate the contacts prepared by magnets 610 and 016.

Immediately that the connection is made at the sender selector switch, a circuit is closed from ground through the left contact of relay 701, conductor 713, conductor 714, contact of selector switch 600, horizontal conductor 635, contact of said selector switch, conductor 636, left normal contacts of relay 532, conductor 227, contacts of selector switch 200, horizontal conductor 240, left-hand winding of magnet 213 to battery. The horizontal magnet 213 is thereby held through its left-hand winding under the control of the sender shown in Fig. 7 and independently of the circuit previously traced through the right-hand winding of said magnet. Moreover, the circuit just traced from ground is further extended by way of the horizontal conductor 240 through contacts of the switch 200 through the test wire 241, winding of relay 232 to battery. Relay 232 operates and extends the grounded conductor 241 through its lower front contact to conductor 135 and through the winding of relay 119 and also through the line switch 100 to the windings of magnet 106 and the cut-off relay 104. to battery.

The lower contact of relay 232 is of the make-before-lncak character whereby the circuits of magnet 106 and relays 104 and 119 are completed by way of conductor 241 to ground at the contact of relay 701 prior to the opening of the original circuits. Relay 232, at its upper contacts, disconnects the trunk 115 from the sender in Fig. 4 and relay 400 becomes deenergized. Relay 400 releases and after an interval relay 401 retracts its armatures. Relay 401 removes ground from conductor 417. and thereby the horizontal magnet 337 becomes dcencrgized and the sender selector switch 300 is restored to its normal condition. The removal of ground from conductor 417 also permits the release of relay 315 in order that the vertical magnet 314 may again be selected. The dcenergization of relay 401 and the release of the sender selector switch 300' removes ground from the conductor 235, but, as already seen, the line switch 100 is now held under the control of the relay 701 at the succeeding sender mechanism.

\Vhen relay 401 releases, and upon the disconnects ground potential from condiic-- tor 4,14 and also "from conductor420, where by the previously tracedcircuits of relay 318 and magnet 211 areopenedl- Relay 318 disconnects the testing relay set- "from the group of trunks at the switch 200'and the vertical magnet 211, ondeenergizing, restores the associated operating bar to its normal-position. All test relays 321-, 322, and 323'of-the set of test relays, which have been ener ized through their left-hand are not energized. However, such ofthese' relays as have circuits completed through their right-hand windings through the contacts of the corresponding relays-217, 218, 219 and 220, owingto the 'b'usycondition of theseveral link circuits at the switch 200, will remain operated to indicate this condition when they are nexttaken into use for testing the same or some-other groups of trunks.

It will further be observed that the circuit for the vertical'ma-gnet 236 is also opened.

by the release of relay e03. Magnet 236 be comes deenergized and also restores theassociated vertical bar to its normal position.

Relay 403, on retracting its armature, also removes ground fromconductor 4115, thereby interrupting the circuit of the. vertical magnet 610 at'the sender selector 600. Magnet 610 restores the associated bar to its normal position and. also opens the, circuit of magnet 616'. This latter magnet deenergizes and the associated bar'is returned to normal; However, prior to the release of the vertical magnets 610 and616'controlling the vertical rows of contacts 601 and 605, respectively, the following'circuit has been closed to'include the line relay 7 00 of the sender mechar nisni: battery, through the winding of said magnet, conductor 633, throughthe operated contacts ofthesender selector600', horizontal conductor 637, contacts of switch 600, conductor 638, inner= right contact of relay 532, conductor 226,:through contacts of the selector switch 200, conductor-138, contacts otlineswitch 100, line conductor 103, line conductor 102', through contacts of the line switch 100, conductor 137, contacts of selec-e tor switch 200, conductor 225, outerright cont-act oi -relay 532 to ground. Relay 700 is held in series with the line circuit after the original energizing circuit'for said-relay calling subsciibers line.

The sender selector switch 600-is main tinned in its operated condition by means of I opened at thecontacts of the vertical ,inagnet 616; In this-manner, the control'of a holding time which leads-irombatt'erythrough the winding and inner frontcontact of horizontal magnet 620, through-the contacts of the link circuit 607, the horizon- 3 trunk 115 leadin in to the 'rou selector 200, the sender mechanism of Fig; 1 has'boen associated by the sender selector 200 with the calling line and, in response to thefirst series of impulses, has selected the group of trunks and an idle trunk 221 therein'at the switch 200, thus extending the line through to the second group selector switch 500; In response to the extension of the line to the trunk 221, the sender selector switch 600 has operated to associate the sendermechanism of Fig; 7 with'the extended line following which the first sender mechanism and the sender selector switch 300 were released. The line switch 100, the selector switch 200 and the sender selector switch 600 are maintained in their operated condition under the control of the calling subscribers line through the agency of the impulse relay 700 of the sender mechanism and said mechanism awaits the receipt of the next series of im-' pulses in order to select the desired numericalgroup of trunks at the selector switch 500.

The calling subscrib'crnext transn'iits a series of impulses representing the second digit of the wanted number, which is as sumed to be the digit 3. In response to the first impulse the relay 700 releases its armature and a circuit is closed from ground through the back contact of said relay, right contact of relay 7 0'1, windin-g'of slow-to-re-' lease relay 702 to battery. Relay 702 operates and a circuit is closed from battery through the winding ofslow-to-releaserelay 704, right contact'otrelay 702, left contact of relay 701 to ground. Furthermore, the circuit from ground through the lettcontact ofrelay 700 extends by way of conductor 715, lower back contact of counting relay 7 O5, winding ofrelay 706 to battery. The counting relay 706 operates and upon the termination of'the impulse relay 5 is'op'erated in series therewith in a manner"under stood. During the nextimpulse, the circuit, through the back contact-otrelay 7 00', leads by way of conductor 715, lower front contact tact of counting relay 720, conductor 721,

' of relay 705, lower back contact of relay 707,

winding of relay 708 to battery. At the end of the second 1mpulse,relay 707 operates 111 series with the relay 708 and the counting relays are held by circuits leading to ground at the left contact of relay 701. In response to the third and final impulse of the second series, counting relays 720 and 723 are operated and locked to ground at the left contact of relay 701.

After thelapse of the usual interval following the second series of impulses, the relay 700remains energized for a sufficient time to cause the release of the slow relay 702. Relay 702, at its right contact, opens the circuit of relay 704. Belay 7041-, how ever, being slow to release maintains its armature attracted for an appreciable interval after the release of relay 702. Relay 702 also completes a circuit from battery through the winding of relay 7 03, left contact of re lay 702, uppermost contact of relay 705, front contact of relay 700 to ground. Relay 703 operates and closes a circuit from ground through its contact, conductor 716, conductor 717, contacts of link circuit 607, conductor 639, winding of vertical magnet 506 to battery. Magnet 506 rotates the associated bar and prepares the contacts of the incoming trunk 221 for connection with any one of the horizontal link circuits in the selector switch 500.

Relay 703 also completes a circuit from ground through its contact, conductor 716,

contacts of the horizontal link circuit 607,

V conductor 64:0. winding of multi-contact relay 709 to battery. Relay 709 operates and closes a holding circuit from battery through its winding and contact, conductor 719, conductor 713, to ground at the left contact of relay 701. Relay 709, in operating, associates the counting relay set of the sender mechanism with the particular selector switch 500 shown, to which leads the incoming trunk 221.

Relay 703 also closes a circuit from ground through its contact, inner upper con tact of counting relay 705, upper front con tact of counting relay 7 07 upper back concontacts of relay 709, conductor 722, thence in parallel through the windings of relay 628 and vertical magnet 509 to battery. The multi-contact relay 628 operates in this circuit and in the manner well understood as- .sociates the left-hand winding of the testing relays 622, 623, 02 1, 625, 626 and (327 with the test conductors of the numerical group of outgoing trunks appearing in the vertical row 505 at the selector switch 500. The vertical magnet 509 controlling this group of-trunks is also operated and rotates the associated bar to prepare the contacts of the trunks for connection with the horizontal link circuits. Assume that all trunks 520, 521 and 522 in the group preceding the trunk 519 or the corresponding llOliZOIltnl link circuits 530, 533 and 531 are busy or both trunks and links are busy. Hence the relays (327, (326, 625, 02-1 and 623 are all operated due to circuits either through their right-hand windings or left-hand windings or both, and the relay 622 is the lirst deenergized relay in the set. The deenergized condition of relay 622 represents that the trunk 515) and also the horizontal link 529 having access to this trunk are both simultaneously idle.

The interval following the release of relay 702, during which the test is made. ha iing elapsed, the slow relay -1- retracts its arniature and a. circuit is established as follows: ground, through the contact of relay 7023, contact of relay 70-1 conductor 712, left front contacts of relays (327, (S20, (S25, 02 1 and 623, left back contact of relay ($22, con ductor 64.1, right-hand winding of horizontal magnet 511 to battery. Magnet 511 operates and is held temporarily in a locking circuit which may be traced from battery through the right-hand winding and contact of said magnet, conductor 530, cont-acts of relay 700, conductor 713 to ground at the left contact of relay 701. The magnet 511 rotates the associated bar and closes the contacts of the link circuit 525) which eooperate with the contacts or" the incoming trunk 221 and of the outgoing trunk 510.

through contacts of relay 628, conductor 612,

and thence to the vertical magnet at the next sender selector switch similar to switch 600 controlling the vertical row of contacts in which appears the selected trunk 510.

The manner in which the next sender selec'tor switch is operated will be obvious from the description licrcinbei'ore given of the switches illustrated in delailf immediately that the sender selector switch at the next stage operated, a ground potential is extended back over the test conductor of the trunk 51!) through contacts of the switch 500 to hold the horizontal magnet 511 operated. Moreover, this ground is extended through the contacts of switch 500, conductor 537, winding of relay 532 to battery. Relay 532, at its left front contact, extends the grounded conductor 537 to the conductor 227, whereby the line switch 100 and selector switch 200 are held in an operated condition under the control of the succeedlng sender mechanism prior to the 

